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High-sugar diets found to significantly reduce the lifespan of flies

Flies with a history of eating a high sugar diet live shorter lives – even after their diet improves – an international study involving Monash University has found.

This is because an unhealthy diet drives long-term reprogramming of gene expression, according to a study published today in Cell Reports.

The study discovered that the action of a gene called FOXO is inhibited in flies given a high-sugar diet in early life, causing long-term effects. The FOXO gene is important for longevity in many species, including yeast, flies, worms – and humans.

“The findings improve our understanding of how changes in diet and gene expression affect the speed of ageing,” said Monash ARC Future Fellow, Dr Matt Piper, one of the key authors of the study.

“This is further evidence of how excess sugar in the diet is detrimental to health,” he said.

The study, led by University College London (UCL) found that excessive sugar in the early adult fly diet curtailed survival in middle and old age.

The research team compared the lifespans of female flies fed a healthy diet containing 5% sugar to those given eight times this amount. The flies, which live to about 90 days on average, were fed both diets for three weeks before all were given a healthy diet.

Even while feeding on a healthy diet, the flies that had previously eaten a high-sugar diet started to die earlier, and on average had 7% shorter lifespans. This was caused by a change in the programming of the flies’ physiology caused by the sugar-rich diet eaten in early adulthood.

To understand how the high sugar diet affected longevity, the scientists analysed the flies at a molecular level. They found the unhealthy diet promoted molecular changes that looked very much like flies with genetically reduced FOXO.

Importantly, further experiments showed that the diet-driven changes to lifespan are dependent on FOXO.

The work was funded by the Biotechnology & Biological Sciences Research Council, Medical Research Council, Royal Society, Wellcome and Australian Research Council.